Establishment of national reference standard of fluconazole impurity h / 中国药学杂志

ABSTRACT

OBJECTIVE: To introduce the procedure of developing reference standards of fluconazole impurities using fluconazole impurity H as an example and reveal a special problem for establishment of national reference standards. METHODS: Firstly, the structure of fluconazole impurity H was validated by infrared, mass spectrum and nuclear magnetic resonance method. Secondly, its purity was determined using the related substances test of fluconazole in European Pharmacopoeia 8.0 (EP8.0) and Chinese Pharmacopeia (2010 version, Volume 2, ChP2010). Then the major impurities determined by the above two HPLC systems were analyzed by LC-MS method. Finally, the content of fluconazole impurity H, its water content and inorganic impurities were determined by quantitative nuclear magnetic resonance (qNMR) method, Karl Fischer titrimetry method and residue on ignition method respectively. RESULTS: The structure of fluconazole impurity H was identical with that in EP 8.0. The contents of water and inorganic impurities were 0.05% and 0.04%, respectively. It was found that fluconazole impurity H would be partially degraded into fluconazole impurity G in water solution, which resulted in the inaccuracy of the related substances test. The content of impurity H was 99.5% by qNMR method. CONCLUSION: Due to the structural characteristics of fluconazole impurity H, the mass balance method, which is the routine method for determination of the content of reference standards, is not suitable for fluconazole impurity H. In the circumstances, qNMR method can be used as a complementary method for the content determination of reference standards.